METHOD AND MEANS FOR ADDITION OF ODOUR COMPONENT TO CONSUMER GAS

Abstract: The invention relates to method and means for addition of odour component to gasline system for consumer gas. A carrier gas (2) is saturated with an odour component by conducting the carrier gas through a container (3) with liquid odour component and the amount of consumer gas is monitored by a flowmeter (5) which gives signal to a registration/steering unit (7) which regulates the amount of mixed gas, carrier gas-odour component. The pressures in the gaslines (1, 6) for consumer gas and mixed gas are monitored and the mixed gas is supplied to the gasline for consumer gas when the pressure difference between the two lines is within a predetermined range. Registration of the pressure difference gives signal to the registration/steering unit (7).

Description: Method and means for addition of odour component to consumer gas The present invention relates to a method for addition of odour component to a gas, comprising addition of the odour component to the main gasline for this consumer gas. The invention also comprises means for carrying out the method. Supply of gas to place of consumption is for several purposes made by means of a gasline system and one should then be able to register possible leakages to the surroundings. One way of securing such undesired leakage of gas is to add an odour or aroma component to the gas. In several cases it is desired to add the odour component to the gas at its production site. In these cases one desires to add the odour component into the gasline system. Examples of gases for which the present method can be applied are oxygen for instance to welding, burning and heat treatment, and gases for packaging of foodstuff. There exist several odour/aroma components which can be applic¬ able for the purpose, some of these might be toxic and it is then essential that the aroma component is added in correct amounts such that during gas leakage the concentration of odour component does not become too high. It has further been a problem to attain secure handling and storage of toxic odour components. Some odour components can also result in undesired condensation, corrosion, etching etc. Dimethylsulphide (DMS) is one example of such an odour component recommended for oxygen gasline system. According to Rules of Law for working environment published by the Norwegian Directorate for inspection of working conditions, "Addition of odour component to oxygen for welding, burning and heat treatment", DMS shall be added to the oxygen pipeline system in amounts of 10-30 mg/Nm 3 . According to known technique described in the above instructions of 7 December 1979, liquid DMS is pumped from a tank by means of dosage pump. DMS is added to the oxygen through an evaporator which consists of a sintered metal body moistened by DMS, said body is placed in the gas stream. The temperature of the oxygen should be kept at 10-20°C ahead of the injection zone in order to prevent condensation of DMS. This technique has several disadvan¬ tages, especially with regard to precise dosages, security and operation. The dosage pump is accordingly representing a problem. Too much DMS in the oxygen makes the gas explosive. The object of the present invention was to arrive at an improved method of supplying the odour component into the gasline system of the consumer gas and that this method should not have the disadvantages mentioned above. A further object was to arrive at means which operationally were simpler and more secure than those means applied today. During the development of the new method the inventor found that several of the problems related to the known method were connected to application of liquid odour component. Gasification of the odour component prior to injection into the gasline system was investigated, but was found to imply that several of the problems of the known method still would remain. It was then found that by diluting the odour component with an inert carrier gas one could easier secure precise dosage of the odour com¬ ponent. If one in addition let the odour component evaporate into the carrier gas, it would be possible to avoid pumping of liquid odour component. This would simplify the means and apparatus to be used and in addition one would avoid the problems which could arise in the pump, for instance due to its lubricating oil. By leading the carrier gas directly into a container with liquid odour component at a predetermined temperature one could obtain a mixture of gases having desired concentration of the odour component. Precise dosage of the odour component and thereby the prescribed concentration in the consumer gas could be secured during application of conventional apparatus components. It was further found that the addition of odour component could be secured if the pressure in the gasline system for the consumer gas and in the line for the mixture of carrier gas-odour component were measured. The pressure in the latter line should always be largest and it was secured closure of supply of odour component regulated by a predetermined pressure difference ΔP. The special features of the invention and its scope are as defined in the attached claims. The invention will now be further explained in connection with the description of the means for performing the method. Fig. 1 shows means according to the invention. Gas from a storage tank (not shown) is supplied to the gasline system for the consumer gas, for instance 0 2 , through line 1. The amount of this gas is registered by a flowmeter 5 and the pressure in line 1 is registered by a DP-cell which also measures the pressure in line 6 through which a mixture of odour component and inert carrier gas is flowing. The respective pressures Ε>→ι and P 2 and P 2 - P i = ΔP are registered and shown in the registra¬ tion/steering unit 7. An alarm (not shown) will start at a predetermined ΔP and thereby stop the supply of odour component to line 1. The mixed gas can for instance flow through line 6 when 1.5 bar < ΔP < 2.5 bar. The inert carrier gas can be argon or helium and in certain cases nitrogen and is supplied through line 2. The carrier gas is mixed with a gaseous odour component from the container 3. This is preferably done by letting the carrier gas in the container 3 be saturated with the gaseous odour component which at least is present in the upper part of the container 3. In the lower part of container 3 the odour component might be present in liquid form. The amount of the mixture of odour component and carrier gas in line 6 is measured by means of flowmeter 8 and this measurement is monitored by the registration/steering unit 7. The amount which leaves through line 6 can thereby be regulated as the unit 8 also comprises a control unit. The mixture of carrier gas-odour component is conducted through line 6 and fed directly into line 1 and thereby one obtains rapid and complete mixture of the odour component in the consumer gas which thereupon can be conducted into the consumer line through line 11. Check valves can be placed both in lines 1 and 6. By the present invention one has obtained several advantages and simplifications relative to known technique. The odour component can be injected into the consumer gas precisely and in a secure way. Even though the odour component which at normal pressure and temperature is liquid one does not have any problem with condensation at the injection site in the gasline system for the consumer gas. Application of pumps which increases the cost of the apparatus is avoided and the risk for operational stops and leakage of odour component which might be toxic and etching is reduced. Applications of such odour components are possible by using the present invention because the container for the odour component is connected directly to the inert gasline and the line for mixed gas. The operator of the apparatus will thereby not be exposed to extra danger such as loss of liquid and leakages of such liquid. By the present invention one also avoids the risks experienced today with regard to explosion/fire which application of liquid DMS now results in. The problems which the above Rules §10 describe with regard to lubricating oils do not exist in connection with the present means which does not comprise pumping of liquid and aggressie odour component.

Claims: Claims Method for addition of odour component to gasline system for consumer gas, comprising addition of odour component in gaseous form in a carrier gas, c h a r a c t e r i z e d i n that the carrier gas is saturated with odour component by conducting the carrier gas through a container with liquid odour component and that the amount of consumer gas is monitored by a flowmeter which gives signal to a registration/steering unit which regulates the amount of mixed gas, carrier gas-odour component, and that the pressures in the gaslines for consumer gas and mixed gas are monitored and that the mixed gas is supplied to the gasline for consumer gas when the pressure differ¬ ence between the two lines is within a predetermined range and that registration of the pressure difference also gives signal to the registration/steering unit. Method according to claim 1, c h a r a c t e r i z e d i n that the mixed gas is supplied to the line for consumer gas when the pressure difference ΔP between the two lines is in the range 1.5 bar < ΔP < 2.5 bar. Means for carrying out the method according to claims 1-2 comprising supply lines for consumer gas (1) and carrier gas (2) and a container (3) for odour com¬ ponent, c h a r a c t e r i z e d i n that the line (6) from the container (3) and through which is transported a mixed gas, carrier gas-odour com¬ ponent, is connected to a DP-cell (4) which also is in connection with line (1) , and that the pressure difference ΔP between lines (6) and (1) is registered by the cell (4) and that the line (1) comprises a flowmeter (5) and line (6) comprises a flowmeter (8) which give signals to a registration/steering unit (7) connected to the cell (4) and that the amount of mixed gas conducted into line (1) at a place subsequent to the flowmeter (5) , is regulated according to the measured values from the units (4) , (5) and (8) . 4. Means according to claim 3 , c h a r a c t e r i z e d i n that the unit (7) comprises an alarm which starts when supply of consumer gas is stopped when ΔP is different from a predetermined value. 5. Means according to claim 3 , c h a r a c t e r i z e d i n that in each line (1) and (6) there are check valves (9) and (10) ahead of the connection point for line (6) to line (1).

Inventors: NILSEN TORBJOERN AARNES, NILSEN, TORBJOERN, AARNES
Applicants: NORSK HYDRO AS, NORSK HYDRO A.S.
Application year: 1994
Main classification: F17D3
IPC codes: C10L3, F17D3, G05D11